The present invention relates to a drive device for an automatic embedding machine for treating samples for histological examinations.
The preparation of tissue samples for histological examinations is carried out by a number of chemical treatments, and the samples are finally embedded in paraffin. For the chemical treatment, the water contained in the sample is first of all withdrawn from the latter and replaced by stabilizers, dyes and the like. Finally, the sample is embedded in paraffin. This means that the paraffin block can be retained in a stable manner in a receiving means of a microtome. So-called automatic embedding machines, which transport the samples automatically to the various treatment stages, have been developed for the various, successive process steps.
DE-B 11 14 338, DE-B 10 97 164, B 10 38 795 and German Patent Specification 878,871 each disclose an automatic embedding machine which is intended for treating samples for histological examinations and in which a plurality of containers arranged one beside the other are provided. The automatic embedding machines also have a plurality of object holders which are fastened, on a lifting device, over the containers. For preparation of the samples, the object holders are immersed into the respective containers via the lifting device. For this purpose, the lifting device has a turntable and a rotatably mounted guide rod.
U.S. Pat. No. 3,809,897 discloses an automatically operating sample-changing machine which is intended for a spectrometer and in which the samples can be changed via a motor-driven cable pull.
DE-A 36 25 695 discloses an apparatus which is intended for cryogenically fixing samples and in which an injector rod with the sample is prevented from rebounding elastically from a low-temperature metal mirror. For this purpose, the longitudinally movable injector rod is connected to a freewheel via a rack and a gear wheel. Once the sample has come into contact with the metal mirror, the freewheel blocks any further movement of the injector rod.
A known automatic embedding machine is described in the document "Jung HISTOKINETTE, Leica Instruments GmbH, list 6008/ND/10/94, October 1994". This automatic embedding machine contains a circular arrangement comprising a plurality of containers for the chemicals as well as heatable containers for the wax. The containers are designed to be open at the top. Provided above the containers is a rotatable plate which has a plurality of sample-receiving means and is connected fixedly to a guide rod. The sample-receiving means can be introduced into the respective containers by virtue of the plate, or the guide rod, being lowered and rotated. Once a programmable period of time has elapsed, the plate, with the sample-receiving means, is raised again, rotated by a certain amount and lowered again into the next container.
In the "HISTOKINETTE", the drive for the guide rod is realized via a motor and an associated gear mechanism. The gear mechanism has an eccentric, and the rotary movement of the latter raises the guide rod and lowers it again. The guide rod is rotated, during its downward movement, by a geared connection to a plurality of linkages. The "HISTOKINETTE" automatic embedding machine has proved successful in practice.
Throughout the process, which lasts a number of hours, the automatic embedding machine generally operates without supervision. In the event of a power failure, there is a risk of the automatic embedding machine stopping midway through operation. If it comes to a standstill during a lifting movement, the ambient air renders those samples which are being processed completely unusable since the geared drive connection of the HISTOKINETTE cannot lower the samples without power.